Angular 1.3 compatibility fix - demo and readme

[pgaertig]

This completes #20 and fixes #28. The README and demo page have contained deprecated usage of the interceptor. That usage is causing apps to fail after Angular 1.3.x fix was introduced (#20). This fix corrects it that growl interceptor works both in AngularJS 1.2.x and 1.3.x.

[JanStevens]

Hello,

So for v1.2.x people should use

$httpProvider.responseInterceptors.push(growlProvider.serverMessagesInterceptor);

For v1.3 people should use

$httpProvider.interceptors.push(growlProvider.serverMessagesInterceptor);

right?

[pgaertig]

With current master for both AngularJS 1.2.x and 1.3.x apps the only correct way to register the growl interceptor is:

$httpProvider.interceptors.push(growlProvider.serverMessagesInterceptor);

$http.responseInterceptors is deprecated in AngularJS 1.2.x. It accepts only function based interceptors. Since #20 the serverMessagesInterceptor is an object and passing it to responseInterceptors array causes $http problems described in #28.

And here is this PR which modifies docs and demo to use the correct way.